MICROBIOLOGY - ALCAMOLECTURE: CRITERIA FOR

PROKARYOTES & EUKARYOTES

Introduction - Cells

• All living organisms have cells

• Basic unit of structure

• Large organisms – many cells

• Cells are organized into:

– Tissues – stomach lining

– Organs – esophagus, stomach, intestines

– Systems – digestive system

MICROORGANISMS

One or a few cells take care of all functions

Prokaryotic Cell:

• No nuclear membrane

• No other internal membranes (no organelles)

• Only has a cell membrane

• Examples – bacteria, cyanobacteria

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PROKARYOTES

- They are very small cells

- They have a very thin cell wall:- Shape - Protection

- They have a cell membrane:- Lines the cell wall

- Regulates molecular traffic

- They have a nucleoid or nuclear region where their one, looped molecule of DNA resides

PROKARYOTES- Their cytoplasm is a soup of chemicals

(including free ribosomes), where all cell activities take place

- They may contain a flagella – a long hair-like appendage made of protein and responsible for motion in MO’s- May have one or many- Made of protein flagellin- Movement is chemically driven - chemotaxis

Eukaryotic Cell:

•Has a nuclear membrane

•Has other membrane bound organelles:

mitochondria

Golgi bodies

endoplasmic reticulum

•Examples – animals, plants, fungi, protozoa, unicellular algae

EUKARYOTES

- They are larger cells than the prokaryotes

- They may have a 3 layer cell wall:- Shape- Protection

- They have a cell membrane: - Lines the cell wall - Regulates molecular traffic

- They have a nucleus with a nuclear membrane:

- Double stranded DNA (chromosomes)

- RNA

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- They have a cytoplasm – Soup of chemicals containing membrane bound organelles for all cell activities

- They may have a flagella –

- cable-like

- Made of tubulin protein

- Arranged in a microtubule array of 9 doublets around 2 singlets

Prokaryotic vs. Eukaryotic CellsCharacteristic Prokaryotes Eukaryotes

Nucleus Absent Present with nuclear membrane

Organelles Absent Present in a variety of forms

DNA Structure Single closed loopNaked strand with no protein

Multiple chromosomesProtein associated with DNA

Chlorophyll When present – dissolved in cytoplasm

When present –contained in chloroplasts

Ribosomes Smaller and free in cytoplasm

Larger and often bound to membranes

Cell walls Present and complex Present /absent and simple

Reproduction Fission – no mitosis Mitosis

Examples Bacteria, Cyanobacteria Fungi, protozoa, plants, animals, humans

Classification of Organisms

-Eukaryotes - all multicellular organisms and unicellular organisms (except 2)

Examples: mammals, fish, plants, fungi, algae and protozoa

-Prokaryotes – (the other 2) only bacteria and cyanobacteria

Microorganism Size

• Micrometer – unit of length most commonly used (1/1,000,000 of a meter)

• MO’s range in size from almost visible protozoa (100um) down to incredibly small viruses (0.01 um)

• Most bacteria are 1 – 5 um in length

Bacteria

• Prokaryotes and one of the most abundant organisms on earth

• Can affect us positively (digest sewage, extract N from air for plants, break down dead and decaying matter)

• Can be harmful to us (produce toxins in our bodies, infect plants and animals, etc)

• Are able to live under almost any conditions (arctic ice, hot springs, ocean trenches, acidic conditions, no oxygen)

Small Bacteria

• Rickettsiae barely seen with light microscope

• Transmitted by arthropods such as ticks and lice

• Can cause Rocky Mountain spotted fever and typhus fever

Small Bacteria

• Chlamydiae – even smaller than rickettsiae and can’t be seen with light microscope– One species causes the gonorrhea-like disease

known as chlamydia

• Mycoplasmas – smallest known bacteria and do not have cell walls– Can cause one form of pneumonia and one type

of sexually transmitted disease

Cyanobacteria

• Used to be known as blue-green algae, but are more closely related to bacteria

• They are prokaryotes and have light trapping pigments for photosynthesis

• Many are blue, but some are black, green or red (Red Sea)

• Inhabit freshwater and marine environments (ponds turn green, need algicide in pools)

Protozoa

• Single celled microscopic eukaryotes

• Some cause diseases such as malaria and sleeping sickness

• Come in many shapes and sizes and some are capable of photosynthesis

• Classified according to how they move (flagella, cilia, cytoplasmic extensions called pseudopodia)

Cilliate Amoeba

Fungi• Primary decomposers of organic matter in

the world

• Can cause human diseases such as athlete’s foot

• Used to be classified as plants but:– Don’t do photosynthesis – must obtain

preformed food– Cells have different cell wall

Fungi

• Eukaryotic organisms – 2 groups:– Yeasts – unicellular, ~ size of large bacteria

• Play a vital role in fermentation of beer and wine and production of bread

– Molds – long chains of cells seen as fuzzy masses

Yeast Mold

Unicellular Algae

• The term algae refers to any plant-like organisms that practice photosynthesis and differ structurally from land plants

• Two important algae for microbiology:– Diatoms – Dinoflagellates

Diatoms

• Eukaryotic marine organisms• They are photosynthetic – make carbohydrates –

passed on to other marine organisms when they are eaten

• Cell walls are impregnated with silicon dioxide (glasslike)

• When they die their remains accumulate on the sea floor as diatomaceous earth (used to produce filters)

Dinoflagellates

• Photosynthetic eukaryotes

• Important in the world’s food chains

• They can also produce periodic red tides in the oceans

Viruses

• Neither prokaryotes nor eukaryotes

• They are non-cellular, do not grow, do not show any nutritional pattern

• Only observable activity is replication, which can only be done inside a living cell

• They are just a fragment of DNA or RNA inside of a protein sheath

• Cause many human diseases – flu, polio, hepatitis, chickenpox